Most important results of SAO RAS for 2025
Here you would find a brief summary of the most important results of scientific research carried out by our researchers during the last year, presented by the observatory to the Department of Physical Sciences of the RAS. Access here the archives of our results from 1993.
Metagalaxy
Extremely Cold Hubble Flow and the Mass of the Local Group
The Local Group of galaxies holds a unique place in our exploration of the Universe. Modern deep surveys provide a continuous stream of high-precision measurements, including distances, the motions of stars and galaxies, the discovery of new satellites, and the detection of faint structural features. Data of comparable quality remain inaccessible beyond the Local Group, making it a unique laboratory for probing the evolution of stellar systems, the distribution of dark matter, and its role in shaping galactic dynamics.
Using the most comprehensive collection of data to date on nearby galaxies, we carried out a detailed study of the velocity field in the neighborhood of the Milky Way and the Andromeda galaxy. This analysis provides a much clearer picture of the dynamics within the Local Group. We obtained new, robust estimates of the total masses of both the Milky Way and Andromeda within their virial boundaries. For the first time, we show that galaxies on the outskirts of the Local Group form an exceptionally “cold” flow, with a remarkably small spread in radial velocities of just 15 km/s—far lower than predicted by standard cosmological models. This discrepancy opens new directions for both theoretical and observational research. This cold Hubble flow extends down to the boundaries of the virial zones of the Milky Way and Andromeda Galaxy. This allowed us to measure the total mass of the Local Group, (MLG = 2.47×1012 M⊙), with a precision of about 6% across a wide range of distances. Remarkably, this total mass is fully consistent with the sum of masses of the Milky Way and Andromeda Galaxy derived from the motions of their satellites. Therefore, our results suggest that nearly all mass of the Local Group is concentrated within the virial regions of these two giant spiral galaxies, placing strong constraints on the distribution of the dark matter in the system.
The work was carried out within the framework of the Russian Science Foundation grant No. 24-12-00277.
Authors:
Makarov D.D., Makarov D.I., Makarova L.N. (SAO RAS), Libeskind N. (Leibniz Institut für Astrophysik Potsdam), Kozyrev K. (SAO RAS, KFU).
Published:
1. Makarov Danila, Makarov Dmitry, Makarova Lidia, Libeskind Noam, “The frozen outskirts: A cold Hubble flow and the mass of the Local Group”, 2025, Astronomy & Astrophysics, 698, id. A178, pp. 8.
2. Makarov Danila, Makarov Dmitry, Kozyrev Kirill, Libeskind Noam, “Line-of-Sight Mass Estimator and the Masses of the Milky Way and Andromeda Galaxy”, 2025, Universe, 11, id. 144.
Details
Detection of radio wave scattering screens towards the quasar 2005 + 403 with long-term RATAN-600 observations
Based on multifrequency measurements with the RATAN-600 radio telescope of the radio-bright quasar 2005 + 403, observed through thermal plasma in the gas-dust region of the Cygnus-X in the interstellar medium of the Milky Way, rare extreme scattering events (ESE) of the source's radio emission were detected for the first time. Three flux-density variations characteristic in shape were detected at frequencies of 4.8, 8, and 11.2 GHz in 2011, 2015, and 2020. These ESEs are approximated by a numerical model of a scattering screen-lens, which yields the following physical properties: the average angular and linear size of the lens 0.3 ± 0.1 mas, i.e., 0.6 ± 0.1 au, the lens proper motion 8.3 ± 0.7 mas per year, and its transverse velocity of 70 ± 6 km/s (the distance to the lens is 1.8 kpc). The electron density along the line of sight was 1200 ± 120 cm−3 and the mass of each lens is (0.8 ± 0.4) 10−15 M⊙. Importantly, the intrinsic (pre-scattering) angular size of the quasar 2005 + 403 was reconstructed as 1.57 ± 0.14, 0.95 ± 0.08, and 0.68 ± 0.04 mas at frequencies 4.8, 8, and 11.2 GHz, respectively. Monitoring of the quasar 2005 + 403 in 2015–2016 first showed that the scattering lenses crossed the quasar's line of sight one after another. As a result, a clearer understanding of the spatial structure of the interstellar medium on the smallest scales was achieved, which in turn defines the undistorted radio properties of microquasars and quasars containing black holes in thermal plasma.
The work was carried out within the framework of the state assignment of SAO RAS.
Authors:
Koryukova T.A. (CrAO RAS, ASC LPI), Trushkin S.A. (SAO RAS), Pashchenko I.N. (ASC LPI), Pushkarev A.B. (CrAO RAS, ASC LPI).
Published:
Koryukova T.A., Trushkin S.A., Pashchenko I.N., Pushkarev A.B. Probing plasma scattering screens towards the quasar 2005 + 403 with long-term RATAN-600 observations, 2025, MNRAS, V. 542, Iss. 4, pp. 2733-2751.
Archive of achievements, Metagalaxy sector
Galaxy
Discovery of unusually strong variability in DDO68-V1, a bright blue variable (LBV) with extremely low metallicity
LBVs comprise a small group of young massive stars in advanced evolutionary stages, during which they lose a significant portion of their mass in winds and during “giant eruptions”. In the LBV phase they spend only a brief part of their lives ending it with a supernova explosion or transitioning to Wolf–Rayet stars. Since most LBVs are found in the Milky Way and nearby massive galaxies, their metallicities are around solar or much lower. A characteristic feature of LBVs is optical variability (of the S Dor-type) on timescales of years with amplitudes up to 1–2 magnitudes, while their bolometric luminosity remains nearly constant. Understanding the influence of massive stars on the evolution of the first galaxies is particularly timely in the context of discoveries made with the JWST space telescope. To understand processes in galaxies of the early Universe, models of massive stars with very low metallicities, characteristic of that epoch, are needed. Validation of such models is possible only on real stars visible in galaxies with extremely low metallicity, which are exceedingly rare in the local Universe.
DDO68-V1, an LBV with record-low metallicity, Z ~ 0.025 Z⊙, is a unique object of the Local Universe. Based on the results of our eight-year photometric monitoring of DDO68-V1 with the SAO RAS and SAI MSU: the BTA, Zeiss-1000, and 2.5-m of CMO, conducted after the giant eruption phase, we first detected a phenomenon of strong brightness variability with an amplitude of 3–3.5 magnitudes on a timescale of about a year. This could be an S Dor-type variability with an amplitude much larger than that of known LBVs or a new type of variability. Its nature is unknown and may be related to the star's extremely low metallicity and/or its state after the giant eruption. This discovery provides insights into the evolution of very low-metallicity massive stars and offers a new impetus for their modeling and interpretation of data on early-Universe galaxies.
The work was carried out within the framework of the state assignment of SAO RAS and partially supported by the Ministry of Education and Science of Russia grant.
Authors:
S.A. Pustilnik, Yu.A. Perepelitsyna, A.S. Vinokurov, A.S. Moskvitin, A.N. Burenkov, O.A. Maslennikova, O.I. Spiridonova (SAO RAS) in cooperation with E.S. Egorova (University of Heidelberg), V.P. Goranski (SAI MSU).
Published:
1. Pustilnik S.A., Perepelitsyna Y.A., Vinokurov A.S., Egorova E.S, Moskvitin A.S., Goransky V.P., Burenkov A.N., Maslennikova O.A., Spiridonova O.I. Monitoring of DDO68 “Northern Ring” SF Regions in 2016-2023, 2024, Astroph. Bulletin, v. 79, 593-612.
2. Pustilnik S.A., Perepelitsyna Y.A. The variability of DDO68-V1, a unique, extremely metal-poor luminous blue variable, 2025, Astronomy & Astrophysics Letters, 695, L7.
V694 Mon: unique observations of dynamical mass transfer between components
V694 Mon is a well-known symbiotic system in which high-velocity gas jets reaching 6500 km/s were previously observed. The earliest images of this system, dating to 1899, were found in the Moscow Astronomical Plate Archives of SAI MSU. Over the next 125 years, its brightness increased by about 100 times. In 2018, the authors of this work detected abrupt changes in its behavior. Follow-up observations over six years showed that the Roche lobe of the compact component—the jet source—became completely filled with the matter flowing from the cool giant. A new photosphere formed in this region corresponding to an A4 I spectral-type star with normal stellar radiation characteristics. A particularly important new result was a February 2022 flare of the s-process element emission observed with the SAO RAS 6-meter telescope (BTA). The dynamic mass-transfer mode in such systems had been theoretically predicted, but the rate of its development in V694 Mon proved to be unexpectedly high. For the first time in astrophysics, this process has been traced in such detail. The study yields unique data on the operation of the natural layered thermonuclear source inside the red giant and how its activity products interact with the surrounding environment. Short-lived radioactive isotopes impossible to obtain in laboratory conditions were identified, which is of interest to nuclear physics specialists as well. This study sheds light on a critical phase of evolution for binary systems with dynamic mass transfer and the formation of a common envelope.
The work was carried out within the framework of the state assignment of SAO RAS.
Authors:
Goranskij V.P. (SAI MSU, SAO RAS); Barsukova E.A., Burenkov A.N., Yakunin I.A. (SAO RAS), Metlova N.V., Zharova A.V. (SAI MSU).
Published:
Goranskij V.P., Barsukova E.A., Burenkov A.N., Metlova N.V., Zharova A.V. and Yakunin I.A. V694 Mon: A Recent Event of Mass Transfer in the Dynamical Mode Galaxies V. 13, art. 59. P. 1-13
Details
Archive of achievements, Galaxy sector
Solar system
A robust preprocessing pipeline for RATAN-600 solar radio observations data
The RatanSunPy package was developed—an open-source Python software library designed to access, visualize, and analyze multiband radio observations of the Sun taken with the RATAN-600 solar complex. The package provides a full set of data processing tools including direct access to raw data, key preprocessing steps such as calibration to the quiet-Sun level, and tools for analyzing solar activity. These include automatic detection of local sources, matching them with NOAA (National Oceanic and Atmospheric Administration) active regions, and subsequent determination of the parameters of local sources and active regions. RatanSunPy enables more efficient exploration of the fine structure and dynamics of the solar atmosphere contributing to solar physics research and improving space weather forecasting. RatanSunPy is the first software package for processing solar observations from RATAN-600. The significance of the work lies in the fact that the RatanSunPy package will simplify access to and processing of RATAN-600 solar data potentially increasing research productivity and efficiency. RatanSunPy can be used, with appropriate adaptation, for processing solar radio observations from other telescopes.
The work was supported by RFBR grant No. 24-21-00476.
Authors:
Kurochkin E.A., Shendrik A.V. (SPbU SAO RAS), Knyazeva I.S. (GAO RAS), Derkach D.A. (HSE University), Makarenko N.G. (GAO RAS).
Published:
Knyazeva I., Lysov I., Kurochkin E., Shendrik A., Derkach D., Makarenko N., RATANSunPy: A robust preprocessing pipeline for RATAN-600 solar radio observations data, Astronomy and computing, 2025, v. 51, DOI: 10.1016/j.ascom.2024.100918.
Archive of achievements, Solar system sector
Hardware and methodological developments
Method for Fast Radio Burst (FRB) search in RATAN-600 surveys using a convolutional neural network
Since 2017, a search for fast radio bursts (FRBs)—bright short-timescale impulsive events (<1 ms) subject to cosmic dispersion—has been conducted in RATAN-600 surveys of sky regions at different declinations using four four-channel radiometers in the 4.4–5 GHz range. To automate FRB detection, observation records are scanned with a convolutional neural network, whose task is to identify FRBs in the presence of radio frequency interference and high radiometer noise. The neural networks used for 2D image classification, common in worldwide practice, are not applicable to our data due to the lack of a second coordinate (four channels instead of several thousands). Based on the EfficientNet family, we developed our own neural network for classifying multichannel time series using one-dimensional convolutions taking into account the data array's specifics and reducing the number of trainable parameters.
To suppress false positives, a cascaded scheme of two neural networks is used, where the second network is designed to verify candidates provided by the first network. This reduced false positives to the order of 0.0005% (the exact value is adjustable via the probability threshold). Such a low rate is necessary due to the large number of records processed by the network—the scanning process is performed by splitting the time series into one-second segments.
The method is capable of detecting FRB signals even at levels comparable to system noise. The developed neural network can be applied to classify any multichannel time series in other scientific and applied tasks.
The work was performed under the state assignment of SAO RAS.
Authors:
Kudryavtsev D.O., Trushkin S.A., Tsybulev P.G., Stolyarov V.A. (SAO RAS).
Published:
Kudryavtsev D.O., Trushkin S.A., Tsybulev P.G., Stolyarov V.A., Neural networks in the search for fast radio bursts with RATAN-600, Astronomy and Computing, 2026, Volume 54, id. 101002.
Implementation of a New Decimeter Two-Frequency Radiometer Based on a Horn Antenna with a Common Phase Center
At RATAN-600, a decimeter two-frequency radiometer covering 13 cm and 21 cm bands (with 100 MHz bandwidths) was developed and put into round-the-clock observations. Under the SAO RAS technical assignment, a dual-band horn antenna with a shared phase center (by FSUE SKB IRE RAS) and ultra-low-noise amplifiers, bandpass filters, and directional couplers (by the Research and Production company Micran JSC, Tomsk) were developed and designed. The radiometer replaced the previous-generation receivers at 13- and 25-cm wavelengths and enabled observations with the maximum possible sensitivity for an uncooled radiometer, up to 10 mJy in spectral flux density. The implementation increased the number of detectable radio sources several-fold. The radiometer is used in routine observations of compact and extended radio sources, with capabilities for active digital interference mitigation, fast radio-burst searches, 21-cm neutral hydrogen-line spectral observations, pulsars, and more.
The work was carried out within the framework of the state assignment of SAO RAS.
Authors:
Tsybulev P.G., Nizhelsky N.A., Prizov P.V., Kratov D.V., Udovitsky R.Yu., Sotnikova Yu.V., Borisov A.N., Khapaev A.A. (SAO RAS).
Details
Archive of achievements, Instrumental and Methodological Development sector
Astronomical education
Archive of achievements, Astronomical education sector